MOTHER'S DAY can be particularly devastating for parents of migrant children.

Last September, I met Mathy, a Sri Lankan refugee in California. Mathy told me her family had been hiding in a tiny apartment in Bangkok.

Early one morning, when she stepped out, immigration police raided and took her four daughters, the youngest being 8 years old, to the infamous Bangkok Immigration Detention Center.

Mathy voluntarily joined her daughters in detention. In the two days they were apart, Mathy said, "I wasn't able to sleep, I'd hear them talking like they were calling me, knocking at the door."

Detained in a cell with them and, at times, more than 100 other migrants, Mathy struggled to protect her children when fights broke out between detainees and guards. They were held for two years before the United States eventually resettled them.

Tens of thousands of children every day are in immigration detention around the world.

Arif, an Afghan boy, was detained in Indonesia when he was just 15. "There were eight or nine people beating me," he said. "Most were guards."

Other boys held there told me they had been in detention for months without even being able to call home and let their families know where they were.

At 14, Qiao traveled unaccompanied from China to the United States. Smugglers kept her locked up for long periods during her nine-month journey across five countries. One night, she had to fend off a sexual assault from a drunken and violent trafficker.

Some mothers, like Qiao's, make the difficult decision to send children to migrate alone, leading to parents' anguish if something goes wrong.

Over and over again, mothers tell me of the pain they feel when they can't ensure their children's basic well-being.

The United Nations estimates that worldwide, 5 million children have migrated irregularly — with their families or unaccompanied.

The U.S. government expects that the number of unaccompanied children trying to reach the United States will spike, from 6,560 in 2011 to 60,000 this year.

Migrant children — alone or with their families — frequently risk life and limb in their journey, whether trekking across deserts, hiding in wheel wells or riding unseaworthy boats.

Families don't make decisions to migrate lightly.

I spoke with Reza, a slim-shouldered 14-year-old Afghan boy with traces of a mustache on his upper lip, in an abandoned house under a bridge in Greece. His father had died, and he, his mother and sisters had been living in poverty in a desolate camp in Iran. They decided Reza should go to Europe to support his remaining family.

Children like Arif, Qiao and Reza — and mothers like Mathy — deserve compassion, not incarceration.

On this Mother's Day, let's demand that governments ensure that social welfare ministries — and not immigration departments — address migrant children's needs.

On this Mother's Day, let's insist that governments increase efforts to support unaccompanied children, including ensuring they don't face criminal penalties for illegal entry.